Preparation of dimethyl sulfate



- To all whom it ma concern:

UNIT-ED s;rArss* PA ENT OFFICE.

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- Be it known t at we, WALTER NORMAN HAWORTH and JAMES COLQUHOUN Invnvn,subjects of the King of Great Britain, .residing at St. Andrews,Fifeshire, have invented certain new and useful Improvements in andRelatingrto the Preparation of Dimethyl Sulfate,- of.'which thefollowing is a specification.

This invention has for its object the manu-- facture of dimethylsulfate. 4 Theprocess consists in the union of dimethyl ether withsulfur trioxid by direct means, and under selected conditions;

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We have discovered that combination of .of 80 .1 We got over thisdifiiculty at first fby pouring the crude roduct on to powdered ice, aswarm H S 4 destroys-dimethyl sulfate, but at ice temperature this is notthe casefl The use of ice is expensive and. inconvenient sowe reduce theremaining S0 using a slight excess beyond that required theory.Filtration or decantation then gives us a crude dimethyl sulfate whichserves for all purposes almost as well as the pure product, and moreoverit distils easily and without decomposition under diminished pressureto" give the pure colorless dimethyl sulfate.

We further find that we can dilute our stream of'SO with advantage, andlead this mixture into the solvent (dime thyl sulfate previouslyrovided) and in this form there is no troub e with SO crystallizin inthe leading tubes. The source of-our 0 has in this series oleum which wehave heated to distil over the S0 and this is betterconveyed along theleading tubes by bubbling aslow current of dry air'through the uppersurface of the oleum. The residual sulfuric acid can be Specification n1Letters Patent.

Scotland,

a very with a reducing agent such as iron filings, which we stir in atthe end ofthe reaction the outlet pipe of experiments been- 20% non ormianrnyr, suirnm oleum.

dimethyl sulfate.

We may therefore in practice pass the mixtureof. air, S0 and S0(WhlChI'QSllltS from the contact process of makingSO directly intodimethyl sulfate, and lead inb a separate inlet pi dimethyl ether e 0)in approximate required by the equation below mo-p-soa-mesoq.

, Patented Dec. 27; 1921. Application filed uovem ei 19, ms. Serial- No.268,239..

Sulfur dioxid has little for no fi'ect on y the proportions The air and:30 thus pass on through the liquid, and, after suitable bafliing toremove 4 any vapor of Me, ,SO carried over this mixture of S0 and aircan be conveyed back to the .catalyzing chamber and more SO, made or'theSO' may be absorbed in a solventor led to waste. Thus there is nonecessity to distil oleum as'the source of S0 and the process is all theless dangerous t carry out, as oleum distillation may give troublevunless carefully ontrolled.

qm'pe Fifty grams ofv preformed ldimethyl suifate were placed in avessel; in which were arranged two leading tubesyflipping below thesurface of the liquid.- Through one of these tubes a stream ofdiniethylether gas was admitted, and through the other a current ofsulfur trio'xidvapor the latter vapor may be mixed with air-as an 'aidtoits trans miss'ion,or it may be contaminated with sulfu'r dioxid and airin the in which it is generated by known catiiilytic processes. .Duringthe passing of the' g a ses the liquid medium is agitate or stirred, andthe. rate of admission is regulated ingspch amanner that no escape ofdimethyl ether or of sulfur trioxid occurs from the outlet at the top ofthe vessel. As a precautionary measure, from the upper part of thevessel maybe led intoanother. such vessel 1 also containing preformed.dimethyl sulfate, so that comlplete absorptionwill be assured. Thecontro of the gases andivapo'r is so arranged that approximatelyequimolecula'r quantities of dime'th oxid pass into -;theliquid mediumofdimethylthe containing sulfate simultaneously, and

yl ether and sulfur trivessel is kept cool by an outer-jacket orinternal coil through which cold water ci'rcu:

lateso Immediate combination of the two reagents occurs with theformation of constantly increasin quantities of dimethyl sulfate,so'that t e initial quantity of grams serving as solvent or medium gainsgreatly in hulk. By: introducing another tuloe into the vessel,quantities of the crude product can he'drawnlofi from time to time,continuous overflow of the dimethyl sulfate as more of it is formed. B Ifollowing this procedure the process can e run continuously over aprolonged and indefinite period. As no loss of the reagents occurs, thisheingaided by having suitable water cooled condensing plant, thereaction is almost quantitative. There are practically no secondaryreactions which interfere withthe process under these conditions but itis.

essential that the dimethyl ether and all dl other gases should beperfectly dry and free from alcohol before-admission. In this way, andWOI'kllIl% in small laboratory apparatusexperimenta more than 200 gramsof crude dimeth l sulfate can easily be made in the course 0 a day.Larger scale working is merely a matter of expansion of the size ofvessel and feeds, with appropriate increase of the initial amount ofdimethyl sulfate used as solvent medium. 1

An alternative scheme of working which was found to give good results,although not so convenient, was to pass the sulfur trioxid into thesolvent medium .until a considerable amount had accumulatedinthe'solution, and

then pass in the dimethyl ether as as a separate operation, or viceversa, ut in these cases the process requires more careful control toavoid loss of reagents.

After reducing the crude product with the aid of iron filings or othersuitable reducing agent it is then only necessary to rectify it underdiminished pressure to ohtain pure dimethyl sulfate,

e declare that what we claim is l. A process of preparing dimethyl 'sul-A I ence of previously or an arrangement can he provided, for the n fatewhich consists in directly coinhining dimethyl ether and sulfur trloxidin the presence of a solvent initially comprisingdimethyl sulfate,

2. A process of preparing dimethyl sulfate which consists in directlycombining dimethyl ether and sulfur trioxid' in presitself and anotherdiluent,

3. The continuous process for the ration of dimethyl sulfate whichconsists in simultaneously passing gaseous dimethyl ether-and gaseoussulfur trioxid into dimethyl sulfate initially present as a diluent.

"lxA process of fate which consists dimethyl ether with gaseous" formand performing the reaction in presence of dimethyl sulfate" itself as ain l directly combining which comprises simultaneously passing into asolvent dimethyl ether and a mixture of 'air, sulfur dioxid, and sulfurtrioxid, resulting from the contact fur trioxid. p

In witness whereof, we have hereunto signed our names this 25th day ofOctober, 1918, in the presence of two subscribing witnesses. A

WALTER NORMAN nawonr n JAMES cononrronn rnvrnn Witnesses:

ALLAN Barren, Susan H. 1?. Low.

process of making sulprepa preparing dimethyl sulprovided dimethylsulfate all sulfur trioxid in dilute preparing diinethyl $111 I

